The inventive concept relates to a flash memory device, and more particularly, to a flash memory device revising a program voltage, a three-dimensional (3D) memory device, a memory system, and methods of programming the memory devices.
Recently, there has been increasing demand for a nonvolatile memory device which is capable of being programmed and erased electrically and which does not require refreshing by having data re-written periodically. As a method of programming the nonvolatile memory device, an incremental step pulse programming (ISPP) method is widely used. According to the ISPP method, a program operation is performed by constantly increasing a program start voltage to correspond to a step voltage. However, when the ISPP method is used when a threshold voltage distribution of a memory cell is heterogeneous, a threshold voltage distribution margin may decrease, and thus, errors may occur.